linux-kernel - Re: [RFC PATCH v5 086/104] KVM: TDX: handle ept violation/misconfig exit

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Message-ID: <a6e31fb0-02af-676d-10d5-8afcf73d098d@intel.com>
Date:   Thu, 7 Apr 2022 09:09:02 +0800
From:   Xiaoyao Li <xiaoyao.li@...el.com>
To:     Sagi Shahar <sagis@...gle.com>,
        "Yamahata, Isaku" <isaku.yamahata@...el.com>
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        isaku.yamahata@...il.com, Paolo Bonzini <pbonzini@...hat.com>,
        Jim Mattson <jmattson@...gle.com>,
        Erdem Aktas <erdemaktas@...gle.com>,
        Connor Kuehl <ckuehl@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>
Subject: Re: [RFC PATCH v5 086/104] KVM: TDX: handle ept violation/misconfig
 exit

On 4/7/2022 4:50 AM, Sagi Shahar wrote:
> On Fri, Mar 4, 2022 at 12:23 PM <isaku.yamahata@...el.com> wrote:
>>
>> From: Isaku Yamahata <isaku.yamahata@...el.com>
>>
>> On EPT violation, call a common function, __vmx_handle_ept_violation() to
>> trigger x86 MMU code.  On EPT misconfiguration, exit to ring 3 with
>> KVM_EXIT_UNKNOWN.  because EPT misconfiguration can't happen as MMIO is
>> trigged by TDG.VP.VMCALL. No point to set a misconfiguration value for the
>> fast path.
>>
>> Signed-off-by: Isaku Yamahata <isaku.yamahata@...el.com>
>> ---
>>   arch/x86/kvm/vmx/tdx.c | 40 ++++++++++++++++++++++++++++++++++++++--
>>   1 file changed, 38 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
>> index 6fbe89bcfe1e..2c35dcad077e 100644
>> --- a/arch/x86/kvm/vmx/tdx.c
>> +++ b/arch/x86/kvm/vmx/tdx.c
>> @@ -1081,6 +1081,40 @@ void tdx_deliver_interrupt(struct kvm_lapic *apic, int delivery_mode,
>>          __vmx_deliver_posted_interrupt(vcpu, &tdx->pi_desc, vector);
>>   }
>>
>> +#define TDX_SEPT_PFERR (PFERR_WRITE_MASK | PFERR_USER_MASK)
> 
> TDX_SEPT_PFERR is defined using PFERR_.* bitmask but
> __vmx_handle_ept_violation is accepting an EPT_VIOLATION_.* bitmask.
> so (PFERR_WRITE_MASK | PFERR_USER_MASK) will get interpreted as
> (EPT_VIOLATION_ACC_WRITE | EPT_VIOLATION_ACC_INSTR) which will get
> translated to (PFERR_WRITE_MASK | PFERR_FETCH_MASK). Was that the
> intention of this code?

No. It's a mistake. We have corrected internally you can find corrected 
code in github repo or see it in next version.